This invention relates to an apparatus and method for making an attachment, such as an annular reinforcement, to a predetermined location on a flexible sheet, e.g. around the periphery of an aperture in the sheet.
Although the invention is applicable to a number of uses, a specific application of the invention concerns stitching, in a predetermined manner, a circular (annular) piece of reinforcing fabric around a vent hole in one of the major parts of a safety air bag. Those skilled in the art will recognize other uses, such as adding parts to the air bags, or more generally, to the addition of pieces which require precise placement onto flexible sheets of fabric or the like for other purposes.
Such air bag devices are known. They are actuated in case of an accident, usually in response to rapid deceleration of the vehicle to which they are fitted, so as to deploy in front of the head and upper torso of a driver or passenger in the vehicle. It is necessary that after deployment, the air bag release so as not to impede egress (or rescue efforts) for the person. To that end, the air bags are fitted with one or more vent openings which allow the inflation gas to escape from the bag at a predetermined rate. In some forms, the vent hole may be controlled by a flap valve or the like. Thus, the exact area of the aperture or vent opening is quite important, as is the fact that this vent size be maintained before and during use of the air bag, and that any attachment be precisely and securely fastened in place.
In air bag design, reinforcements are prescribed by material and vent size and width of the reinforcement, i.e. its overlap of the bag material around the vent aperture. Also, the manner of attachment, e.g. type, location, and number of stitches in a sewn attachment, are pre-ordained. With current and future efforts to fit air bags to many more vehicles, there is a need to automate, or at least partially automate, the fitting and attachment of these vent reinforcements, as well as other fabric attachments for the air bag and its major material. Thus, in this use alone there is a need for the present invention.